Testing battery materials to UL standards
UL94 flammability tests, thermal cycling and accelerated aging help engineers evaluate and select the right safe materials for batteries, while also preparing the data needed when the product applies for certification for export.
In a battery pack, ancillary materials such as adhesives, tapes, foams and insulating sheets account for only a small share of the cost but have a major impact on certification results. A material that fails to meet its flammability rating or ages too quickly can force a complete redesign.
UL94: the benchmark for flame resistance
UL94 classifies the flammability of plastic and polymer materials. A specimen is ignited with a standard flame, then the self-extinguishing time and flaming drips are measured.
| Rating | Method | Key requirement |
|---|---|---|
| HB | Horizontal burn | Burning rate below the specified limit |
| V-2 | Vertical burn | Self-extinguishes within 30 seconds, flaming drips allowed |
| V-1 | Vertical burn | Self-extinguishes within 30 seconds, no flaming drips that ignite cotton |
| V-0 | Vertical burn | Self-extinguishes within 10 seconds, no flaming drips that ignite cotton |
| 5VA | Stronger flame | No burn-through, intended for equipment enclosures |
Note that a UL94 rating is tied to a specific thickness. A material rated V-0 at 3 mm will not necessarily be V-0 at 0.5 mm, so always check against the thickness actually used.
Thermal cycling and thermal shock tests
Thermal cycling simulates day-night temperature changes and charge-discharge cycles. A common range is -40 °C to 85 °C or 105 °C, repeated for 500 to 1,000 cycles. After testing, engineers check adhesive bond strength, cracking and delamination, and changes in thermal conductivity.
Damp heat and chemical aging
- Damp heat at 85 °C, 85% RH for 1,000 hours to evaluate hydrolysis.
- Electrolyte immersion for materials at risk of contact.
- Glycol coolant testing for materials near the cooling plate.
- Measurement of dielectric strength and insulation resistance before and after aging.
How AMS supports the testing process
AMS provides UL Yellow Card file numbers for materials, test data from manufacturers and samples in sufficient quantities for customers' in-house testing. When needed, we connect customers with the manufacturers' laboratories for in-depth testing.
A useful practice is to build a material matrix at the start of the project, specifying location, required UL94 rating, thickness and the end-product standard such as UL 2580 or UL 9540. This matrix helps avoid discovering an unsuitable material after the certification file has already been submitted.
Contact AMS Vietnam to receive a catalog of UL-certified battery materials and the accompanying technical documentation.
